1. Field of the Invention
This invention generally relates to a rolling contact bearing assembly, and, in particular, to a crossed-roller retainer for use in a crossed-roller type rolling contact bearing assembly.
2. Description of the Prior Art
A crossed-roller type bearing assembly is well known in the art, and it generally includes a stationary member provided with a V-shaped groove and a moving member also provided with a V-shaped groove opposite to the V-shaped groove of the stationary member. A plurality of rollers are interposed between the stationary and moving members as fitted in and in rolling contact with the V-shaped grooves of the stationary and moving members, thereby allowing the moving member to move relative to the stationary member in the direction parallel to the longitudinal direction of the V-shaped grooves. The rollers fitted in a roller runway defined by the oppositely arranged V-shaped grooves are arranged such that the two adjacent ones are oriented with their axes of rotation extending perpendicular to each other when viewed in the longitudinal direction of the roller run way. It is called the crossed-roller type because the axes of rotation of the two adjacent rollers are crossed.
Also provided in such a crossed-roller type bearing assembly is a crossed-roller retainer for retaining the rollers in position. Such a retainer is normally in the shape of a plate and it is provided with a plurality of holding holes spaced apart from each other. In the prior art crossed-roller retainer for retaining the rollers in the crossed arrangement, the holding holes were formed by machining with plastic deformation, and the peripheral walls of the holding holes formed in the retainer plate were almost perpendicular to either surface of the retainer plate. However, since the rollers placed in the holding holes of the retainer plate are inclined with respect to either surface of the retainer plate, each of the rollers defines a line contact with the wall of the corresponding one of the holding holes. Such a line contact between the roller and the wall of the holding hole, however, is not advantageous because of lack of stability. In particular, in the case of a miniature type bearing assembly, this can be critical because the retainer plate in this case is very thin and in the order of 0.2 mm for the rollers having the diameter of approximately 2 mm and there is a possibility of rollers slipping away from the retainer plate. Besides, the prior art retainer plate was low in dimensional accuracy largely due to the fact that it was machine-processed. Such a low dimensional accuracy could then cause an increase in resistance force.